1. Field of the Invention
The present invention relates to a projector having a control board for importing image information to project an optical image in accordance with the image information, and a projection lens composed of a plurality of beam-condensing elements.
2. Description of Related Art
Conventionally, a projector has been used for presentation at a conference, scientific society and exhibition. Such projector forms an optical image by modulating a light beam irradiated by a light source with an optical modulator in accordance with image information to enlarge and project the optical image.
Ordinarily, a projector has a projection optical system constructed by zoom-magnification-converting lenses and focus-adjusting lenses for enlarging and projecting an optical image modulated by the optical modulator, the mutual position of the lenses being changed to convert the magnification and adjust the focus of the projected image.
A lens-barrel for housing such projection optical system is constructed by a metal component for securing strength against external force.
Further, size and weight reduction is required for improving performance and enhancing portability of the projector, so that the electronic components constituting the projector come to be highly densely installed.
Such projector has a control board installed with a CPU for control and arithmetic processing, thereby controlling the optical modulator etc. in accordance with the image signal inputted from the outside.
The CPU, memory etc. installed on the control board continually consume electric current at a high frequency, causing strong radiation of electromagnetic wave.
Further, electronic components such as a power source having a transformer for transforming a voltage inputted from the outside into a predetermined voltage and a lamp driving circuit are provided on the projector, the electric components such as the power source and the lamp driving circuit also generating strong radiation of electromagnetic wave.
In order to avoid electromagnetic interference of the electromagnetic radiation to the electronic components inside the projector or the other electronics on the outside of the projector, the electronic components of the control board and the inside of the projector are electromagnetically shielded by a shield member made of aluminum etc. and/or an exterior case of metal or synthetic resin plated with metal.
However, on account of design of the shield component attached to the electromagnetic wave radiation and arrangement for enhancing shielding performance, the shielding structure becomes complicated and hinders size reduction of projector.
In order to reduce the size of the projector, the shield member around the control board may be removed. However, since the lens-barrel of the projection lens is made of metal, when the control board and the lens-barrel come close with each other, the circuit elements such as CPU and memory installed on the control board electromagnetically couple with the lens-barrel and, when the lens-barrel is resonated, secondary radiation of electromagnetic wave is caused with the lens-barrel as an antenna. Similarly, when the other electronics components constituting the projector and the lens-barrel of the projection lens are adjacently provided, the electronics components and the lens-barrel are electromagnetically coupled, thus causing secondary radiation of electromagnetic wave.
Accordingly, electromagnetic interference is caused on the electronic components inside the projector or the electronics outside the projector by the secondary radiation of the electromagnetic wave generated by the lens-barrel.
Further, when the lens-barrel of the projection lens is made of metal, the weight of the lens-barrel increases, thus spoiling weight reduction of a projector.
An object of the present invention is to provide a projector capable of preventing secondary radiation of electromagnetic wave caused by inside components to avoid electromagnetic interference while achieving size and weight reduction.
A projector according to an aspect of the present invention has: an electric optical device that modulates a light beam irradiated by a light source in accordance with image information; a projection lens that enlarges and projects the light beam modulated by the electric optical device; and a control board that controls the electric optical device in accordance with the image information, where the projection lens has a plurality of beam-condensing elements and a lens-barrel that houses the plurality of beam-condensing elements, where the control board is disposed adjacent to the projection lens, and where the lens-barrel is made of non-metal member.
The non-metal member may preferably be a plastic member such as polycarbonate and Cool Poly (RS007).
According to the present invention, since the control board for controlling the electric optical device in accordance with image information is provided, the control board being located adjacent to the projection lens composed of a plurality of beam-condensing elements and a lens barrel that houses the plurality of beam-condensing elements, the lens barrel being made of the above plastic member, the weight of the lens barrel can be reduced, thus reducing the weight of the projector.
Further, if the shield member provided adjacent to the control board is removed for reducing the size of the projector, since the lens barrel is made of the above plastic member, there is no electromagnetic coupling between the lens barrel and the circuit elements such as CPU and memory even when the circuit elements such as the CPU and memory installed on the control board and the lens barrel are closely located, thereby avoiding secondary radiation of the electromagnetic wave caused when the lens barrel is electrically resonated to work as an antenna.
Further, even when the other electronics component constituting the projector and the lens barrel of the projection lens are closely disposed, there is no electromagnetic coupling between the other electronics components and the lens barrel of the projection lens, thereby preventing influence of the secondary radiation of the electromagnetic wave from the lens barrel on the circuit elements installed on the control board such as CPU and memory, thus avoiding disturbance of projected image and malfunction.
Accordingly, the size and weight of the projector can be reduced and secondary radiation of the electromagnetic wave by the lens barrel in which the projection lens is housed can be avoided, thus sufficiently preventing electromagnetic interference.
In the projector of the present invention, the control board may preferably be located along a plane defined by an optical path from the light source to the projection lens, the control board planarly covering the lens barrel.
According to the above arrangement, since the control board is disposed along the plane defined by the optical path from the light source to the projection lens, the thickness of the projector can be reduced.
Further, since the control board is disposed to planarly cover the lens barrel, the accommodation efficiency of the control board can be improved, thus enhancing size reduction of the projector.
In the projector of the present invention, the distance between a circuit element installed on the control board and the lens barrel may preferably be within forty millimeters.
Usually, the shorter the distance between the components that radiates electromagnetic wave and the component as an antenna for receiving the electromagnetic wave, the more likely electromagnetic coupling is caused, and the antenna component causes secondary radiation of the electromagnetic wave by resonation after receiving electromagnetic wave of a predetermined frequency.
When the lens barrel is made of metal and no shield member is interposed between the lens barrel and the control board, the distance between the circuit elements radiating electromagnetic wave and the lens barrel has to be set sufficiently wide.
Since the lens barrel is composed of non-metal member as an insulator, even when the distance between the circuit element and the lens barrel is within forty millimeters, the lens barrel does not work as an antenna for the circuit elements that radiates electromagnetic wave, thereby causing no secondary radiation of the electromagnetic wave.
Further, even when the lens barrel is disposed adjacent to the other electronics components, the lens barrel does not work as an antenna for the electromagnetic radiation from the other electronics components, thus avoiding influence of the secondary radiation of the electromagnetic wave on the CPU or memory on the control board located closely to the lens barrel, thus preventing disturbance of projected image and malfunction.
Accordingly, the circuit elements and the lens barrel can be closely located within forty millimeters, the design inside the projector can be facilitated and the size of the projector can be reduced.
In the projector according to the present invention, an optical component casing that houses optical components disposed on an optical path from the light source to the electric optical device may preferably be provided, where a base end of the lens barrel may preferably be fixed to a head formed on the optical component casing, the head being formed of a non-metal member.
The non-metal member may preferably be a plastic member such as polycarbonate and Cool Poly (RS007) as described above.
According to the above arrangement, since the base end of the lens barrel is fixed to the head formed on the optical component casing and the head is made of the above-described plastic member, the head does not work as an antenna for the electromagnetic wave radiated by the circuit elements on the control board or the other electronics components inside the projector, thereby preventing secondary radiation of the electromagnetic wave by the head.
Further, since the head is made of the above-described plastic member, the weight of the head can be reduced, thus reducing the weight of the projector.
In the projector of the present invention, a cooling fan may preferably be located adjacent to the lens barrel.
Since the internal components are installed with high density in accordance with size reduction of the projector, heat is likely to reside inside the projector.
Since the cooling fan is located adjacent to the lens barrel, the temperature of the lens barrel can be prevented from becoming high on account of the heat conduction or thermal radiation from the heating element disposed inside the projector, thus preventing physical deformation of the lens barrel on account of high temperature of the lens barrel.